A process for separating and removing analysis-hindering cells, other than target molecules, is required in order to precisely and rapidly perform molecular analysis of bio-samples.
Cells and cell suspensions are separated using a centrifuge in the related art, but there are drawbacks in that (1) high-priced apparatuses are required to perform pre-treatment and (2) it is difficult to transport the apparatuses.
A current particle separation method using microfluid dynamics may be broadly classified into an active separation method and a passive separation method.
In the active separation method, particles are separated using an external energy field such as an electric field. Representative examples thereof may include capillary electrophoresis and dielectrophoresis separation methods.
Capillary electrophoresis is frequently used to separate materials having polarity, such as proteins or DNA, according to size, but has drawbacks in that a high voltage is required during separation and in that non-polar particles such as cells cannot be separated.
On the other hand, a difference in the dielectrophoretic performance of particles exposed to a non-uniform electric field, depending on the size and the kind of the particles, is used in the dielectrophoresis separation method. Accordingly, there is a merit in that non-polar molecules or cells are capable of being separated without a pre-treatment process. However, the dielectrophoresis separation method may cause electrolysis in an electrolyte solution such as a cell medium, and accordingly has a problem in that a cytophilic solution cannot be used as a separation solution. Further, in the case of a biological sample such as a cell, the applied voltage may affect the activity of the cell, thus limiting the use of the resultant separated material for the purpose of cell therapy.
Unlike the active separation method, the passive separation method has a merit in that microparticles are separated without an additional apparatus other than a microflow channel by using flow energy for sample supply.
Therefore, recently, various microfluid systems adopting the aforementioned merit have been actively studied. Examples thereof include a separation method using a difference in position of particles, which are arrayed depending on the size of the particles in a microchannel (Japanese Registered Patent No. 2005-205387).
However, the passive separation method has a problem in that the microflow rate must be precisely controlled between a sample flow and a sheath flow in order to array the particles at the same initial position in the microflow channel before the particles are separated.
Further, a cell separation element, such as an inertial fluidic element and a hydrophoretic element based on microfluidics has been developed, but the developed elements have a drawback in that efficiency depends greatly on the driving flow rate of the element.
Specifically, the hydrophoretic element has low cell removal efficiency when the flow rate is increased, and the inertial fluidic element has low cell removal efficiency when the flow rate is reduced.
Therefore, there is a problem in that a special high-priced syringe pump having high flow-rate precision is required in order to drive the hydrophoretic element or the inertial fluidic element.
Further, additional electric or physical energy is required in order to manipulate biological microparticles such as cells and DNA. In order to use additional energy, a separate energy source apparatus must be provided to a microfluidic element, and accordingly, a complicated manufacturing process is inevitable.
Therefore, since the manufacturing process and the operation mechanism of the microfluidic element are complicated, there is a limit in the extent to which the portability and the practicality of the element can be increased.
Accordingly, there is a demand for a highly portable and practical apparatus for separating microparticles from a fluid containing the microparticles regardless of a flow rate, and for a separation method using the same.